Tuesday, May 17, 2011

Ballooning spiders

Fear not, ye arachnophobes. The subject of this entry is indeed about spiders, but the star of the show is about as cute as a spider can get. And you'll want to know what we're about to learn...

On my recent West Virginia foray, we were strolling down a seldom-used lane, when a bright yellow object caught our eye. It was a goldenrod crab spider, Misumena vatia, on top of a post! Not only that, she - it is a girl - was acting extraordinarily goofy. The spider would stilt up as high as she could go on her legs, weave back and forth, jig side to side, and otherwise engage in what appeared to be spider break-dancing.

Click the pic for expansion, and you can see two columns of silk issuing from her spinnerets. This is an important point, as we set about determining what this non-web-making spider is doing.


So fixated was our spider on her task that she even rejected what would seem to me to be a perfectly scrumptious meal. This little caterpillar climbed rapidly up the post and directly towards the spider on what seemed to be a certain suicide mission. "Ah, this should be interesting" thought I. The caterpillar threaded right between the spider's legs, paused, apparently came to its senses, and shot back down the post as if it had been ejected from a cannon.

This is why this group of flower spiders gets the badge "crab" spider. When poised for action, they resemble little long-legged crustaceans, and nothing - on their scale at least - will escape that embrace. That's why I figured she was fixated on some mission when she allowed the tasty hotdog-like caterpillar to go free.

Most spiders have eight eyes, as does the goldenrod crab spider. You can see 'em all, right there, like tiny pepper grains outlining that raised area on the spider's "forehead". This is the business end of the spider, and she was presenting it to your blogger when I moved in a bit too close for her comfort. She couldn't have done much to me, but you gotta admire her pluck for not backing down from a 250 pound humanoid.

Back to the mystery. All I could figure was that her strange gymnastics were part of some courtship ritual; an attempt to woo an unseen male suitor. But that didn't seem right, as in the spiders that I know something of, it is the male who does the wooing.


So, I e-mailed my friend Dr. Richard Bradley, who resides right here in Ohio and is the state's foremost expert on arachnids. Perhaps the country's top expert for that matter, and Rich's field guide to spiders of North America will appear within the year, I believe. You'll hear more about that here, when the book is released.


Anyway, I described to Rich what I saw, and shared some photos. Rich's explanation surprised me: the spider was preparing to "balloon". Ballooning is a common tactic among many spiders for dispersing themselves. A spider that wishes to travel scales to the top of some breezy summit, whether it be a fence post, tree branch, automobile roof, and starts to unfurl strands of silk. At some point, the silken chutes will catch the breeze to the point that the spider will be carried aloft.


I knew that tiny spiderlings balloon very commonly as way of dispersing from their natal homesite, but spiderlings are elfin in the extreme. This goldenrod crab spider was a chunk in comparison, and I didn't know that larger adults would also employ ballooning to shift locations. Apparently, all of its abdomen wriggling and funny movements helped to release the soon to be solken parachute strands in just the right way.

Photo: Richard Bradley


Rich sent me this photo of an adult wolf spider in the genus Pardosa, doing just what my spider was doing. It is also on top of a postlike object, and one that is apparently a favored launching pad for ballooning spiders. Note the shimmer of silk at the spider's feet, from previous jumpers.


I suppose, if one is arachnophobic, that the information we have just learned is rather horrifying. What could be worse than spiders drifting through the air, ready to land in your hair? And drift they do, to the tune of millions if you take into account all of the tiny spiderlings that are ballooning about.


As Rich Bradley says, for much of the warmer months, there is a "gentle rain of spiders" floating through the air.

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8 comments:

nina said...

A gentle rain of spiders...what a warm and fuzzy (and eight-legged) to hang onto!
I've often noticed strands of silk flying loosely in the air. Now I will be sure to check to see who's hanging onto the end.

troymullens said...

Great post (no pun intended). I love to see ballooning spiders. I really like crab spiders, except when they catch some of my favorite hairstreak butterflies.

OpposableChums said...

Fascinating. I had no idea. Thanks.

Wren nests in... said...

We see wafts of ballooning spiders in the fall, drifting past the Cape May Hawk Watch. Very fascinating, indeed!

Jack and Brenda said...

Very interesting information.

Beyond My Garden said...

Very interesting. I have never seen (or noticed one of those - and I am in West Virginia!
nellie

Kim said...

Love the pictures and the educational post. I've never heard of ballooning by spiders before -- I'll tuck this in my brain and hope it comes up as a question on Jeopardy sometime!

dennis@dwlvideo.com said...

I was lucky enough to find such a spider and video its efforts. The result is at http://dwlvideo.wordpress.com/2012/06/15/3d-spider-ballooning/